Late Quaternary climate variability as recorded by micropalaeontological diatom data and geochemical data in the western Ross Sea, Antarctica

Abstract

Cores acquired from the Ross Sea continental shelf and continental slope during the XXX Italian Programma Nazionale di Ricerche in Antartide (PNRA) were analysed and yielded interesting micropalaeontological, biostratigraphic diatom results and palaeoceanographic implications. These multiproxy analyses enabled us to reconstruct the glacial/deglacial history of this sector of the Ross embayment over the last 40 000 years, advancing our understanding of the Last Glacial Maximum (LGM) environmental and sedimentological processes linked to the Ross Sea ice sheet/ice shelf fluctuations in a basin and continental-slope environment, and allowed us to measure some of the palaeoceanographic dynamics. The central sector of the Ross Sea and part of its coast (south of the Drygalski Ice Tongue) enjoyed open marine conditions in the pre-LGM era (27 500-24 000 years BP). The retreat of the ice sheet could have been influenced by a southward shift of a branch of the Ross gyre, which triggered early deglaciation at c. 18 600 cal BP with a significant Modified Circumpolar Deep Water inflow over the continental slope at c. 14 380 cal BP. We assume that a lack of depositional material in each core, although at different times, represents a hiatus. Other than problems in core collection, this could be due to the onset of modern oceanographic conditions, with strong gravity currents and strong High Salinity Shelf Water exportation. Moreover, we presume that improvements in biostratigraphy, study of reworked diatom taxa, and lithological and geochemical analyses will provide important constraints for the reconstruction of the LGM grounding line, ice-flow lines and ice-flow paths and an interesting tool for reconstructing palaeosub-bottom currents in this sector of the Ross embayment.

Environmental and Oceanographic Conditions at the Continental Margin of the Central Basin, Northwestern Ross Sea (Antarctica) Since the Last Glacial Maximum

“…In this unit we detected the maximum values of ADA and ASA as previously reported in studies performed on cores from the northwest Ross Sea cores [11,15,25,78,92]. The increase in siliceous microfossil concentration testifies to an increase in primary productivity, also indicated by the presence of the phytodetritus benthic foraminifera E. exigua [93].…”

“…The same environmental condition is also reported as a result of the analysis of core J3 collected in the outer section of the JOIDES Basin [25], where the granulated facies representing a lift-off zone or the presence of thin water film [73] is coeval to our unit. The sediments deposited in the Central Basin were therefore likely deposited under strong glacial influence and in the vicinity of the ice shelf calving zone (sensu [77]), as also proposed by [11,15] at nearby locations.…”

“…The Ross Sea continental margins record the variation of the Antarctic Ice Sheet (AIS) due to the presence of the largest ice shelf, the Ross Ice Shelf (RIS), which promotes the production of dense shelf water which is the precursor for Antarctic Bottom Waters (AABW) [4]. The RIS dynamics that occurred during the Pleistocene and Holocene have been extensively studied in the continental shelf (e.g., [5][6][7][8][9]), whereas the marginal areas including the continental slope and rise area, have been less investigated (e.g., [10][11][12][13][14][15][16]).…”

Post‐LGM Grounding‐Line Positions of the Bindschadler Paleo Ice Stream in the Ross Sea Embayment, Antarctica

“…Several previous investigations of WAIS retreat have focused on western and central Ross Sea troughs (i.e., Drygalski, Joides, Pennell, and Glomar Challenger Basins, see Figure 1a) (e.g., Bart et al, 2011;Bart & Owolana, 2012;Howat & Domack, 2003;Licht et al, 1999;Shipp et al, 1999;Tolotti et al, 2013). Fewer studies have focused on eastern Ross Sea troughs (e.g., Whales Deep and Little America Basins).…”

Glacial–interglacial records from sediments in Powell Basin, Antarctica

“…2011, Tolotti et al . 2013). Biological productivity at the surface is closely related to the distribution of sea ice, and diatoms in underlying sediments can record changes in sea-ice extent.…”